Note: Descriptions are shown in the official language in which they were submitted.
Z006209
,~
IM-0106
~ ' '~
THE VSE OF HIGH PERCENT SOLIDS
FOR IMPROVE~ LIQUID TONER PREPARATION ~--
5DESCRIPTION
TECHNICAL FIE~
This invention relates to an improved process for
the preparation of toner particles. More particularly
this invention relates to a process for the
10 preparation of toner particles in a liquid medium for -
electrostatic imaging. -~
BACKGRQU~D OF THE INVENTION
It is known to develop a latent electrostatic
image with toner particles dispersed in an insulating
nonpolar liquid. Such dispersed materials are known
as liquid toners or liquid developers. A latent
electrostatic image may be produced by providing a
photoconductive layer with a uniform electrostatic
charge and subsequently discharging the electrostatic
charge by exposing it to a modulated beam of radiant
energy. Other methods are known for forming latent -
electrostatic images. For example, one method is
providing a carrier with a dielectric surface and
transferring a preformed electrostatic charge to the i
surface. Useful liquid toners comprise a
thermoplastic resin and nonpolar liquid. Generally a
suitable colorant is present such as a dye or pigment.
The colored toner particles are dispersed in the
nonpolar liquid which generally has a high-volume
resistivity in excess of 109 ohm centimeters, a low
dielectric constant below 3.0 and a high vapor
pressure. The toner particles are <30 ~m determined
by Malvern 3600E Particle Sizer described below. -
After the latent electrostatic image has been formed, ~-
35 the image is developed by the colored toner particles `
'' '
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,
dispersed in said nonpolar liquid and the image may
subsequently be ~ransferred to a carrier sheet.
There are many methods of making liquid toners.
In one method of preparation of the improved toner
particles are prepared by dissolving at an elevated
temperature one or more polymers in a nonpolar
dispersant, together with parl:icles of a pigment,
e.g., carbon black. The solution is cooled slowly,
while stirring, whereby precipitation of particles
occurs. It has found that by repeating the above
process some material was observed that was greater
- than 1 mm in size. By increasing the ratio of solids
to nonpolar liquid the toner particles can be
controlled within the desired size range, but it has
been found that the density of images produced may be
relatively low and when a transfer is made to a
carrier sheet, for example, the amount of image
transferred thereto may be relatively low. The
particles in this process are formed by a
precipitation mechanism and not grinding in the
presence of particulate media and this contributes to
the formation of an inferior toner.
In another method of preparation of toner
particles, the plasticizing of the thermoplastic
polymer and pigment with a nonpolar liquid forms a gel
or solid mass which is shredded into pieces, more
nonpolar liquid is added, the pieces are wet-ground
into particles, and grinding is continued which is
believed to pull the particles apart to form fibers
extending therefrom. While this process is useful in
preparing improved toners, it requires long cycle
times and excessive material handling, i.e., several
pieces of equipment are used.
20~iZ09
In yet another method of preparation of toner
particles for electrostatic imaging, the following
steps are followed:
A. dispersing at an elevated temperature in a
vessel a thermoplastic resin, a nonpolar liquid having
a Kauri-butanol value of less than 30, and optionally
a colorant, at a total % solids of less than 18% by
weight by means of moving particulate media whereby
the moving particulate media creates shear and/or -
impact, while maintaining the temperature in the
vessel at a temperature sufficient to plasticize and
- liquify the resin and below that at which the nonpolar
liquid boils and the resin and/or colorant, if
present, decomposes,
B. cooling the dispersion to permit
precipitation of the resin out of the dispersant, the
particulate media being maintained in continuou~
movement during and subsequent to cooling whereby the
toner particles are <30 ,um determined by Malvern 3600E
Particle Sizer described below and a plurality of
fibers are formed, and
C. separating the dispersion of toner
particles from the particulate media. This method can
provide toners with a particle size of 10 ,um or less
25 as determined by Malvern 3600E Particle Sizer but ~-
requires extremely long grinding times to achieve this
desired particle size.
It has been found that the above disadvantages
can be overcome and toner particles prepared by a
process that does not require excessive handling of
! ~ toner ingredients at elevated temperatures whereby
toner particles having an average size (by area) of 10
,um or less determined by Malvern 3600E Particle Sizer
are dispersed and formed in the same vessel with
greatly reduced grinding times. Transfer of an image
20~6%~g
of the so prepared toner particles to a carrier sheet
results in transfer of a substantial amount of the
image providing a suitably dense copy or reproduction.
SUMMARY QE THE_I~YENTIO~
In accordance with this invention there is
provided a process for the preparation of toner
particles for electrostatic liquid developers
comprising:
A. dispersing at an elevated temperature in a
vessel a thermoplastic resin, and a hydrocarbon liquid
having a Kauri-butanol value of less than 120, at a
- total % solids of at least 22% by weight by means of
moving particulate media whereby the moving
particulate media creates shear and/or impact, while
maintaining the temperature in the vessel at a
temperature sufficient to plasticize and liquify the
resin and below that at which the hydrocarbon liquid
boils and the resin decomposes,
B. cooling the dispersion to permit
precipitation of the resin out of the dispersant, the
particulate media being maintained in continuous
movement during and subsequent to cooling whereby
toner particles having an average by area particle
size of 10 ~m or less, and
C. separating the dispersion of toner -
particles from the particulate media.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings which form a part of
this invention include:
FIG. 1 is a plot of particle size (~m) at cool
grind (hours) for a developer composition of the :
invention illustrated in Example 1 having 30% solids
by weight and a similar plot of the developer
composition having 20% solids by weight (control);
4 ;
;~) [)62~)9
, - ~ .
FIG. 2 is a plot of particle siæe (llrn) at cool
grind (hours~ for another developer composition of the
invention illustrated in Example 2 having 30% s~lids
by weight and a similar plot of the developer
5 composition having 15P6 solids by weight (control); and
FIG. 3 is a plot of par~:icle size (~lm) at cool
grind (hours) for still another developer composition
of the invention illustrated in Example 3 having 30%
solids by weight and a similar plot of the developer
10 composition having 2096 solids by weight (control).
DETAILED DEScRL~TIQN OF TH~ lNVENTION
The process of this invention results in toner
particles adapted for electrophoretic movement through
a hydrocarbon liquid, generally a nonpolar liquid.
The toner particles are prepared from at least -~
one thermoplastic polymer or resin, suitable colorants -
and hydrocarbon dispersant liquids as described in -`
more detail below. Additional components can be
added, e.g., charge director, ad~uvants, polyethylene,
20 ~ine particle size oxides such as silica, etc.
The dispersant hydrocarbon liquids are, prefer-
ably, nonpolar branched-chain aliphatic hydrocarbons
and more particularly, Isopar~)-G, Isopar(~-~, Isopar~-
K, Isopar~g)-L, Isopar~)-M and Isopar(~-V. These
25 hydrocarbon liquids are narrow cuts of isoparaffinic
hydrocarbon fractions with extremely high levels of
purity. For example, the boiling range of Isopar(~-G
is between 157C and 176C, Isopar(~})-H between 176C
and 191C, Isopar~)-K between 177C and 197C,
30 Isopar(~-L between 188C and 206C and Isopar(~)-M
between 207C and 254C and Isopar(~-V between 259.4C
and 329.4C. Isopar~)-L has a mid-boiling point of
approximately 194C. Isopar(~-M has a flash point of
80C and an auto-ignition temperature of 338C.
35 Stringent manufacturing specifications, suc~ as
209
sulphur, acids, carboxyl, and chlorides are limited to
a few parts per million. They are substantially
odorless, possessing only a very mild paraffinic odor.
They have excellent odor stability and are all
manufactured by the Exxon Corporation. High-purity
normal paraffinic liquids, Norpar~12, Norpar~13 and
Norpar~15, Exxon Corporation, may be used. These
hydrocarbon liquids have the following flash points
and auto-ignition temperatures:
Auto-Ignition
Li~uidFlash Point (C! Tem~ (C)
Norpar~12 69 204
Norpar~13 93 210
Norpar~15118 210
Additional useful hydrocarbon liquids are
Aromatic~ 100, Aromatic~ 150 and Aromatic~ 200,
manufactured by Exxon Corp., Houston, TX. These
liquid hydrocarbons have the following Kauri-butanol
values tASTM D1133), flash point, TTC, C (~STM D56),
and vapor pressure, kPa at 38C (ASTM D2879).
Kauri- Flash Vapor
Ll~~nQl ~int ~ressure
Aromatic~ 100 91 43C 1.7 `;
Aromatic~ 150 95 66C 0.5
Aromatic~ 200 95 103C 0.17
All of the dispersant hydrocarbon liquids have an
electrical volume resistivity in excess of 10 ohm
centimeters and a dielectric constant below 3Ø The
vapor pressures at 25C are less than lO Torr.
Isopar~-G has a flash point, determined by the tag
closed cup method, of 40C, Isopar~-H has a flash
point of 53C determined by ASTM D56. Isopar~-L and
Isopar~-M have flash points of 61C, and 80C, ;
.
~': ' ;~
;~0~21[39
respectively, determined by the same method. While
these are the preferred dispersant nonpolar liquids,
the essential characteristics of all suitable
dispersant hydrocarbon liquids are the electrical
volume resistivity and the dielectric constant. In
addition, a feature of the dispersant nonpolar liquids
is a low Kauri-butanol value less than 30, preferably
in the vicinity of 27 or 28, determined by ASTM D1133.
The ratio of resin to dispersant hydrocarbon liquid is
such that the combination of ingredients becomes fluid
at the working temperature. In use, the hydrocarbon
liquid is present in an amount of 50 to 78% by weight,
preferably 70 to 75% by weight, based on the total
weight of liquid developer. The total weight of
solids in the liquid developer is 22 to 50%, pre-
ferably 25 to 30% by weight. The total weight of
solids in the liquid developer is solely based on the
resin, including components dispersed therein, e.g.,
pigment component, adjuvant, etc.
Useful thermoplastic resins or polymers include:
ethylene vinyl acetate (EVA) copolymers (Elvax~
resins, E. I. du Pont de Nemours and Company,
Wilmington, DE), copolymers of ethylene and an ~-
ethylenically unsaturated acid selected from the class
25 consisting of acrylic acid and methacrylic acid, `-
copolymers of ethylene (80 to 99.9%)/acrylic or
methacrylic acid (20 to 0~)/alkyl (Cl to C5) ester of
methacrylic or acrylic acid (0 to 20%), the
percentages being by weight; polyethylene,
polystyrene, isotactic polypropylene (crystalline),
ethylene ethyl acrylate series sold under the -
trademark Bakelite~ DPD 6169, DPDA 6182 Natural and
DTDA 9169 Natural by Union Carbide Corp., Stamford,
CN; ethylene vinyl acetate resins, e.g., DQDA 6479
Natural and DQDA 6832 Natural 7 also sold by Union
~ ` ' ' . !: ., , ' ~ ' ' ' !, . . .
` ` 20C~626)~
; 8
Carbide Corp.; Surlyn~ ionomer resin by E. I. du Pont
de Nemours and Company, Wilmington, DE, etc., or
blends thereof. Preferred copolymers are the
copolymer of ethylene and an a,~-ethylenically
unsaturated acid of either acrylic acid or methacrylic
acid. The synthesis of copolymers of this type are
described in Rees U.S. Patent 3,269,272, the
disclosure of which is incorporated herein by
reference. For the purposes of preparing the
preferred copolymers, the reaction of the acid
containing copolymer with the ionizable metal
compound, as described in the Rees patent, is omitted.
The ethylene constituent is present in about 80 to
99.9~ by weight of the copolymer and the acid
component in about 20 to 0.1% by weight of the
copolymer. The acid numbers of the copolymers range
from 1 to 120, preferably 54 to 90. Acid No. is
milligrams potassium hydroxide required to neutralize
1 gram of polymer. The melt index ~gtlO min) of 10 to
500 is determined by ASTM D 1238 Procedure A.
Particularly preferred copolymers of this type have an ~;;
acid number of 66 and S9 and a melt index of 100 and
500 determined at 190C, respectively.
In addition, the resins have the following
preferxed characteristics:
1. Be able to disperse the metallic soap,
colorant, e.g., pigment,
2. Be substantially insoluble in the
.
dispersant liquid at temperatures below 40~C, so ~hat
30 the resin will not dissolve or solvate in storage, ;~
! i ' 3. Be able to solvate at temperatures above
50C,
4. Be able to be ground to form particles
between 0.1 ~m and 3.6 ~m, in diameter preferred
size), e.g., determined by Horiba CAPA-500 centrifugal
~' . '''
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automatic particle analyzer~ manufactured by Horiba
Instruments, Inc., Irvine, CA.; and between 1 ~m and
10 ~m, in diameter, e.g., determined by Malve~n 3600E
Particle sizer, manufactured by Malvern, Southborough,
MA.,
5. Be able to form a particle (average by
area) of 3.6 ~m or less, e.g., determined by Horiba
CAPA-500 centrifugal automatic particle analyzer,
manufactured by Horiba Instruments, Inc., Irvine, CA:
solvent viscosity of 1.24 cps, solvent density of 0.76
g/cc, sample density of ~.32 using a centrifugal
rotation of l,000 rpm, a particle size range of 0.01
~m to less than 3.6 ~m, and a particle size cut of 1.0 -
~m, and 10 ~m average particle size determined by
Malvern 3600E Particle Sizer, as described above,
6. Be able to fuse at temperatures in excess
of 70C.
By solvation in 3. above, the resins forming the toner
particles will become swollen or gelatinous.
One or more charge directors as known to those
skilled in the art can be added to impart a charge, as
desired. Suitable nonpolar liquid soluble ionic or
zwitterionic charge director compounds, which are
generally used in an amount of 0.25 to 1,500 mg/g,
preferably 2.5 to 400 mg/g developer solids, include:
negative charge directors, e.g., lecithin, Basic
Calcium Petronate~, Basic Barium Petronate~ , Neutral
Barium Petronate, oil-soluble petroleum sulfonate,
manufactured by Sonneborn Division of ~itco Chemical
Corp., New York, NY, alkyl succinimide (manufactured
by Chevron Chemical Company of California), etc.;
positive charge directors, e.g., sodium dioctylsulfo
succinate (manufactured by American Cyanamid Co.),
ionic charge directors such as zirconium octoate,
copper oleate, iron naphthenate, etc.; nonionic charge
, . ~ . , . . . . - -
20~62(~
directors, e.g., polyethylene glycol sorbitan
stearate, nigrosine, triphenyl methane type dyes and
Emphos~ D70-30C and Emphos~ F-27-85, sold by Witco
Chem. Corp., NY, NY, sodium salts of phosphated mono-
S and diglycerides with unsaturated and saturated acid
substituents, respectively.
As indicated above, colorants, when present, are
dispersed in the resin. Colorants, such as pigments
or dyes and combinations thereof, are preferably `
present to render the latent image visible. The
colorant, e.g., a pigment, may be present in the
- amount of up to about 60 percent by weight based on
the total weight of developer solids, preferably 0.01
to 30% by weight based on the total weight of
developer solids. The amount of colorant may vary
depending on the use of the developer. Examples of
pigments are Monastral~ Blue G (C.I. Pigment Blue 15 ~ ~
C.I. No. 74160), Toluidine Red Y (C.I. Pigment Red 3), ~ `
Quindo~ Magenta (Pigment Red 122), Indo~ Brilliant ;`
20 Scarlet (Pigment Red 123, C.I. No. 71145), Toluidine ;~
Red B ~C.I. Pigment Red 3), Watchung~ Red B (C.I.
Pigment Red 48), Permanent Rubine F6B13-1731 (Pigment
Red 184), Hansa~ Yellow (Pigment Yellow 98), Dalamar~ `; ;
Yellow (Pigment Yellow 74, C.I. No. 11741), Toluidine
25 Yellow G (C.I. Pigment Yellow 1), Monastral~ Blue B `
(C.I. Pigment Blue 15), Monastral~ Green B (C.I.
Pigment Green 7), Pigment Scarlet (C.I. Pigment Red ~`~
bO), Auric Brown (C.I. Pigment Brown 6), Monastral~
Green G (Pigment Green 7), Carbon Black, Cabot Mogul L
30 (black pigment C.I. No. 77266) and Sterling NS N 774
(Pigment Black 7, C.I. No. 77266). ~ ~ `
Other ingredients may be added to the
electrostatic liquid developer, such as fine particle -~
size oxides, e.g., silica, alumina, titania, etc.
preferably in the order of 0.5 ~m or less can be
: '~ .' "
.
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2~ 0~
dispersed into the liquefied resin. These oxides can
be used instead of the colorant or in combination with
the colorant. Metal particles can also be added.
Another additional component of the electrostatic
liquid developer is an adjuvant which can be selected
from the group of polyhydroxy compound which contains
at least 2 hydroxy groups, aminoalcohol, polybutylene
succinimide, metallic soap, and aromatic hydrocarbon
having a Kauri-butanol value of greater than 30. The
adjuvants are generally used in an amount of 1 to
1,000 mg/g, preferably 1 to 200 mg/g developer solids.
Examples of the various above-described adjuvants
include:
p~Qlyhydroxy compounds: ethylene glycol, 2,4,7,9-
tetramethyl-5-decyn-4,7-diol, poly(propylene glycol),
pentaethylene glycol, tripropylene glycol, triethylene
glycol, glycerol, pentaerythritol, glycerol-tri-12
hydroxystearate, ethylene glycol monohydroxystearate,
propylene glycerol monohydroxy-stearate, etc.,
described in Mitchell U.S. Patent 4,734,352;
~ minoalcohol compounds: triisopropanolamine,
triethanolamine, ethanolamine, 3-amino-1-propanol, o-
aminophenol, 5-amino-1-pentanol, tetra(2-
hydroxyethyl)ethylenediamine, etc., described in
Larson U.S. Patent 4,702,985;
~ olybutylene succinimide: OLOA~-1200 sold by
Chevron Corp., analysis information appears in ~osel
.S. Patent 3,900,412, column 20, lines 5 to 13,
incorporated herein by reference; Amoco 575 having a
number average molecular weight of about 600 (vapor
pressure osmometry) made by reacting maleic anhydride
with polybutene to give an alkenylsuccinic anhydride
which in turn is reacted with a polyamine. Amoco 575
is 40 to 45% surfactant, 36~ aromatic hydrocarbon, and
~k :. i -. ,': .. . .- . ' ' .. ' . ... , , . : , . . . .
2(~ 2~9
the remainder oil, etc., described in El~Sayed and
Taggi, U.S. Patent 4,702,984;
metalli~_soap: aluminum tristearate; aluminum
distearate; barium, calcium, lead and zinc stearates;
cobalt, manganese, lead and zinc linoleates: aluminum,
calcium and cobalt octoates; calcium and cobalt
oleates; zinc palmitate; calcium cobalt, manganese,
lead and zinc naphthenates; calcium, cobalt,
manganese, lead and zinc resinates; etc. The metallic
soap is dispersed in the thermoplastic resin as
described in Trout, U.S. Patent 4,707,429; and
- aromati~ hyd~ocarbon: benzene, toluene,
naphthalene, substituted benzene and naphthalene
compounds, e.g., trimethylbenzene, xylene,
dimethylethylbenzene, ethylmethylbenzene,
propylbenzene, Aromatic~ 100 which is a mixture of C9
and C10 alkyl-substituted benzenes manufactured by
Exxon Corp., described in Mitchell U.S. Patent
4,663,264, etc. The disclosures of the aforementioned ~
20 United States patents are incorporated herein by ~ ~ `
reference.
The particles in the electrostatic liquid
developer preferably have an average by area particle
size 10 ~m or less. The average by area particle size
determined by the Malvern 3600E Particle Size Analyzer
can vary depending on the use of the liquid developer.
The resin particles of the developer may or may not be
formed having a plurality of fibers integrally ~
extending therefrom although the formation of fibers -
3Q extending from the toner particles is preferred. The ~-
term "fibers" as used herein means pigmented toner
particles formed with fibers, tendrils, tentacles,
threadlets, fibrils, ligaments, hairs, bristles, or
the like. `
20~
.
13
In carrying out the process of the invention, a
suitable mixing or blending vessel, e.g., attritor,
heated ball mill, heated vibratory mill such as a
Sweco Mill manufactured by Sweco Co., Los Angeles, CA,
equipped with particulate media, for dispersing and
grinding, etc., is used. Generally the resin,
colorant, and dispersant hydrocarbon liquid are placed
in the vessel prior to starting the dispersing step at
a percent solids of at least 22%, preferably 25 to 30%
by weight. Optionally the colorant can be added after
homogenizing the resin and the dispersant hydrocarbon
- liquid. Polar additive can also be present in the
vessel, e.g., up to 100% based on the weight of polar
additive and dispersant hydrocarbon liquid. The
dispersing step is generally accomplished at elevated
temperature, i.e., the temperature of ingredients in
the vessel being sufficient to plasticize and liquefy
the resin but being below that at which the dispersant
hydrocarbon liquid or polar additive, if present,
degrades and the resin and colorant, if present,
decomposes. A preferred temperature range is 80 to
120C. Other temperatures outside this range may be
suitable, however, depending on the particular
ingredients used. The presence of the irregularly
moving particulate media in the vessel is needed to
prepare the dispersion of toner particles. It has
been found stirring the ingredients, even at a high
rate, is not sufficient to prepare dispersed toner
particles of proper size, configuration and
morphology. Useful particulate media are particulate
materials, e.g., spherical, cylindrical, etc. taken
~rom the class consisting of stainless steel, carbon
steel, alumina, ceramic, zirconium, silica, and
sillimanite. Carbon steel particulate media is
particularly useful when colorants other than black
:`. ; ., - ,
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2~)~62~3
14
are used. A typical diameter range for the
particulate media is in the range of 0.04 to 0.5 inch
(1.0 to approx. 13 mm).
After dispersing the ingredients in the vessel,
with or without a polar additive present, until ~he
desired dispersion is achieved) typically 0.5 to 2
hour with the mixture being fluid, the dispersion is
cooled to permit precipitation of the resin out of the
dispersant. Cooling is accomplished in the same
vessel, such as the attritor, while simultaneously
grinding with particulate media to prevent the
formation of a gel or solid mass. Cooling is -~
accomplished by means known to those skilled in the
art and is not limited to cooling by circulating cold
water or a cooling material through an external
cooling jacket adjacent the dispersing apparatus or
permitting the dispersion to cool to ambient
temperature. The resin precipitates out of the
dispersant during the cooling. Typical cooling ~
20 temperatures may range from 15C to 50C. Toner ~ ;
particles of average particle size ~by area) of 10 ~m
or less, as determined by a Malvern 3600E Particle
Sizer, 3.6 ~m or less as determined using the Horiba
centrifugal particle analyzer described above, or
other comparable apparatus, are formed by grinding for
a relatively short period of time when compared with
former methods. It is preferred that the desired
particle size be achieved within a normal work period,
e.g., 8 hours or less, preferably 4 hours or less.
The Malvern 3600E Particle Sizer manufactured by
Malvern, Southborough, MA which uses laser diffraction
light scattering of stirred samples to determine
average particle sizes. Since these two instrument -
use different techniques to measure average particle
size the readings differ. The following correlation
19 ~ ;
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.; ~;
)6209
, _ ,
of the average size of toner particles in micrometers
(~m) for t~e two instruments is:
Value Determined By Expected Range For
Malvern 3600E Particle Sizer Horiba CAPA-SOO
9.9 ~ 3.4
6.9 + l.9
4.6 + 1.3
2.8 + 0.8
10 5 1.0 + 0.5
3 0.2 + 0.6
This correlation is obtained by statistical
- analysis of average particle sizes for 67 liquid
electrostatic developer samples (not of this
invention) obtained on both instruments. The expected
range of Horiba values was determined using a linear -
regression at a confidence level of 95%. In the
claims appended to this specification the particle
size values are as measured using the Malvern
instrument.
After cooling and separating the dispersion of
toner particles from the particulate media by means
~nown to those skilled in the art, it is possible to
reduce the concentration of the toner particles in the
dispersion, impart an electrostatic charge of
predetermined polarity to the toner particles, or a
combination ~f these variations. The concentration of
the toner particles in the dispersion is reduced by
the addition of additional dispersant hydrocarbon
liquid as described previously above. The dilution is
normally conducted to reduce the concentration of
! ' toner particles to between 0.1 to 10 percent by
weight, preferably 0.3 to 3.0, and more preferably 0.5
to 2 weight percent with respect to the dispersant
hydrocarbon liquid. One or more hydrocarbon liquid
soluble ionic or zwitterionic charge director
. ~ , . , -,. .
: . ~: . . . -. . . , . . , . :
, ~, . . . . - : . ~ . - . :
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1 2C~62~9
.
16
compounds of the type set out above, can be added to
impart a positive or negative charge, as desired. The
addition may occur at any time during the process;
preferably at the end of the process, e.g., after the
particulate media are removed and the concentration of
toner particles is accomplished. If a diluting
dispersant hydrocarbon liquid is also added, the ionic
or zwitterionic compound can be added prior to,
concurrently with, or subsequent thereto. If an
adjuvant compound of a type described above has not
been previously added in the preparation of the
developer, it can be added prior to or subsequent to
~he developer being charged. Preferably the adjuvant
compound is added after the dispersing step.
INDUSTRIAL APPLICABI~IT~
The improved process of this invention produces a
liquid electrostatic developer which may have a
plurality of fibers extending from the toner
particles. The liquid developer contains toner ` `
particles having a controlled particle size range
which can be prepared more quickly than by previously
known processes using similar equipment for making
liquid electrostatic developers. The developer is of
the liquid type and is particularly useful in copying,
e.g., making office copies of black and white as well
as various colors; or color proofing, e.g., a
reproduction of an image using the standard colors:
yellow, cyan and magenta together with black as
desired. In copying and proofing the toner particles
are applled to a latent electrostatic image. Other
uses are envisioned for the improved toner particles, ~ -~
e.g., the formation of copies or images using toner -`
particles containing finely divided ferromagnetic
materials or metal powders; conductive lines using
35 toners containing conductive materials, resistors, -
16
.... .
2~)~62~:)9
, "
17
capacitors and other electronic components;
lithographic printing plates, etc.
E ~ PLES
The following examples wherein the parts and
percentages are by we~ght illustrate but do not limit
the invention. In the examples the melt indices were
determined by ASTM D 1238, Procedure A, the average
particle si2es by area were determined by a Malvern
3600E Particle Sizer, manufactured by Malvern,
Southborough, MA., as described above, the
conductivity was measured in picomhos/cm (pmhos) at 5
hertz and low voltage, 5 volts, and the density was
measured using a Macbeth densitometer model RD918.
The resolution is expressed in the Examples in line
pairs/mm (lp/mm).
EXAMPLE 1
Two black liquid developers were prepared by
placing the following ingredients in a Union Process
lS Attritor, Union Process Company, Akron, Ohio:
20 Ing~dient Amount ~g~
S~m~ole 1 2
Copolymer of ethylene (89%)399.2 399.2
and methacrylic acid (11%)
melt index at 190C is 100,
acid No. is 66.
Heucophthal Blue G XBT-583D 1.9 1.9
Heubach, Inc., Newark, NJ
Cabot N-774 Sterling NS carbon92.9 92.9
black, Cabot Corp., Carbon
~lack Division, Boston, MA.
35 Aluminum stearate, Low Gel II,5.0 5.0
Nuodex Inc., Piscataway, NJ
Isopar~-L, nonpolar liquid1167.0 1998.0
having a Kauri-butanol value
40 of 27, Exxon Corporation
2~
18
The ingredients were heated to 100C and milled
at a rotor speed of 230 rpm with 0.1875 inch (4.76mm)
diameter steel balls for one hour. The attritor was
cooled while the milling was continued. Milling was
continued at 50C and at a rotor speed of 340 rpm for
the length of time required to produce similar
particle sizes for Samples 1 and 2. Results are shown
in Table 1 below. FIG. 1 is a plot of particle size
(~m) versus cool grind (hours~. AT 30% solids the
grind time to achieve 6 ~m particle size is 5 hours
versus 21 hours grind time at 20% solids (control). ~`
TABLE 1
GRIND TIME
PARTICLE SIZE TO REACH
SAMPLE % SOLIDS (AFTER 6 HOURS) ~_U2
1 30 5.7 5 HOURS
2 (Control) 20 8.3 21 HOURS
The developer was diluted and charged as follows: ~`
1500 grams of 1.0% solids was charged with 7.5 grams
of 10% Basic Barium Petronate~ oil soluble petroleum
sulfonate, Sonneborn Div., Witco Chem. Corp., NY, NY.
Image quality was determined using a Savin 870 copier `
25 at standard mode: charging corona set at 6.8 Kv and ~ `
transfer corona set at 8.0 KY. Results are tabulated
in Table 2 below. -
TABLE 2 ;
::.
COND DENSITY RESOLUTION
SAMPLE l~mhQL ~EB ~1p/mm) EFFICIENCY ~ aEEB ~ :
! . !
1 16 Savin 1.59 10 67%
Offset 2.05 10 78%
35 2 13 Savin 1.61 10 60%
Offset 2.09 10 74%
18
-
~0~;~09
19
EXAMPLE ~
Two cyan liquid developers were prepared by
placing the following ingredients in a Vnion Process
lS Attritor, Union Process Company, Akron, Ohio:
IngLQçi~ Amount tg)
Sampl~ 1 ~
Copolymer of ethylene t91%)369.3369.3
and methacrylic acid (9%)
melt index at 190C is 500,
Acid No. is 54.
Monarch Blue X3627 pigment,122.9122.9
Ciba-Geiyy, Hawthorne, NY
Aluminum stearate, Low Gel II 5.0 5.0
Nuodex Inc., Piscataway, NJ
Isopar~-L, nonpolar liquid having927.0 1996.0
a Kauri-butanol value of 27, Exxon
Corporation
The ingredients were heated to 100C and milled
at a rotor speed of 190 rpm with 0.1875 inch (4~76mm)
diameter steel balls for one hour. The attr~tor was
cooled while the milling was continued. Milling was
continued at a temperature of 40C and at a rotor
speed of 190 rpm for 3 hours. Results are shown in
Table 3 below. FIG. 2 is a plot of particle size (~m)
versus cool grind (hours). Cyan toner particles are
initially smaller than the black toners of Example 1.
Sample 1 achieves a particle size of 4 ZUm in about 1.5
hours cool grinding whereas Sample 2 reaches 5.2 in 3
hours.
TA~LE ~
35 ~ PARTICLE SIZE
S~MPLE % SOLID$ (~m
1 35 4.0
2 tControl) 20 5.2
19
z~
- ExAMPL~
Two black liquid developers were prepared by
placing the following ingredients in a Union Process
lS Attritor, Union Process Company, Akron, Ohio:
5 Ingredient Amount (gl
Sampl~ 1 2
Elvacite~ 2014, a methacrylate 200.0 200.0
copolymer, E. I. du Pont
de Nemours and Co., -
~ilmington, DE
Uhl.ich BK 8200 35.3 35.3
laked carbon black
Paul Uhlich and Co., Inc.,
Hastings-On-Hudson, NY
Isopar~-L, nonpolar liquid1331.0 786.0
having a Kauri-butanol value -~
of 27, Exxon Corporation
~ .: . , '
The ingredients were heated to 100C and milled
at a rotor speed of 190 rpm with 0.1875 inch (9.76 mm) -
diameter steel balls for one hour. The attritor was
cooled while the milling was continued. Cool milling
was continued at 33C (Sample 1) and 32C (Sample 2)
and a rotor speed of 340 rpm for 5.5 hours. Results
after 0.5 hour cool grinding are shown in Table 4
below. FIG. 3 is a plot of particle size (~m) versus
cold grind (hours). Sample 2 achieves a particle size
of 6 ~m in 0.5 hour cool grinding. Sample 1 (control)
particle size is ~15 ~m in 0.5 hour cool grinding.
TABLE 4 .
PART I CLE S I ZE
35 ~MPLE % SOLIDS (~m)
1 (Control) 15 ~15
2 30 6
1' :,' ~ ' '. ` ' .,;
.", ~ .. ... . . .. . .. .... . . . . . . . . . . .
- - 2~6ZOg
21
~iXAMPLE 4
Two black liquid developers were prepared by
adding 394.2 grams of polystyrene, Aldrich Chemical
Co., Milwaukee, WI having a weight average molecular
weight of 250,000 determined by gel permeation
chromatography (GPC), 99.8 grams of Cabot N-774
Sterling NS carbon black pigment, 5 grams of Aluminum
Stearate, Low Gel II, Nuodex Inc., Piscataway, NJ and
the amount of Aromatic~ 150 petroleum product, Exxon
Corp., Houston, TX to a Union Process lS Attritor,
Union Process Company, Akron, Ohio charged with 0.1875
~ inch (4.76 mm) diameter carbon steel balls. The
mixture was milled at 100C for 1 hour at 230 rpm
then cooled and the mixture was cool milled at 50C
and 230 rpm for 4 hours. The particle size results of
cool milling for 4 hours are set out in Table 5 below.
TABLE 5
AROMATIC~ PARTICLE SIZE
20 SAMPLE ~ % SOLIDS l~mL
1 1167 30 1.8
2 1998 (control) 20 2.7
~8~1E_~
Two yellow liquid developers were prepared by
placing the following ingredlents in a Union
Process 30-S Attritor, Union Process Company, Akron,
OH:
,. ~ . ., . :
~t CJi6~(~9
22
In~ Amount (lb)
SampleL 1 2
Copolymer of ethylene (89~) 14.0 14.0
S and methacrylic acid (11)
melt index at 190C is 100,
Acid No. is 66
Diarylide Yellow AAOT, Y-14, 3.59 3.59
10Polyethylene flushed color,
Sun Chemical Corp.,
Cincinnati, OH
Aluminum Stearate, Low Gel II, 0.36 0.36
15Nuodex, Inc., Piscataway, NJ
Isopar(~-L, nonpolar liquid 102.0 40.0
having a Kauri-butanol value
of 27, Exxon Corporation
The ingredients were heated to 90C and milled at
a rotor speed of 100 rpm with 0.1875 in (4.76 (inch)
diameter steel balls for 2 hours. Temperature was
allowed to increase to 125C during this two-hour
25 period. The attritor was cooled while the milling was
continued. At 65C, 24 lbs of Isopar(~-L was added in
Sample 2. Milling was continued at 35C and a rotor
speed of 100 rpm. Sample 1 was milled at 35C for 10
hours, while Sample 2 was milled at 35C for 4 hours.
30 Results are shown in Table 6 below. For Sample 2 at
about 22% solids during the cool grind, the grind time
required to reach 8.0 llm was 2 hours, versus 10 hours
for Sample 1 (control) at 15~ solids.
TABLE 6
Grind Time
Cool GrindParticle Size to Reach
Sam~ SolidstAfter 4 Hou~i) 8 '~lm
40 1 ~control) 15~ 13.5 ~lm 10 hours
2 22% 7.3 llm 2 hours
